Commitments and Contingencies - Off-balance Sheet Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Off-balance Sheet Risks, Amount, Liability	$ 381	$ 338
Commitments to Extend Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Off-balance Sheet Risks, Amount, Liability	700,986
Performance Letters Of Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Off-balance Sheet Risks, Amount, Liability	25,854
Standby Letters of Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Off-balance Sheet Risks, Amount, Liability	31,754
Other Letters Of Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Off-balance Sheet Risks, Amount, Liability	$ 15